In the production of many products, for instance, writing paper, a web of the sheet material is pulled at high speed from a roll or other supply and is cut longitudinally and transversely into individual sheets that are moved at the high speed to a station where they are stacked. Before they are laid on the stack, the sheets must be braked or slowed considerably from the high speed at which they move upstream.
Systems for doing this are described in German patent document 1,245,702 published Jul. 27, 1967, 1,931,208 of H. Vits published Feb. 24, 1971, 2,330,560 of M. Kubo et al published Jan. 10, 1974, and 2,755,160 of J. Bodewein published Jun. 13, 1979, as well as in German utility models 89 07 553 and 90 07 362, and in PCT application PCT/EP90/02143 of G. Schaffner et al. All of these devices attempt to grip the sheets, typically at their trailing edges, in a braking station immediately upstream of the stacker so the sheets can form an overlapping pile that is fed at low speed to the stacker.
In all known systems the sheets are treated rather roughly so that they can become dog eared or marked. In addition the braking equipment often is a complex mechanical device with differentially moving parts that are prone to failure at best and very expensive at worst. Even when a so called suction box, that is a chamber that is continuously evacuated and that has an upper surface on which a braking belt runs, is used, paper jams are common in that the sheet following a sheet adhered suctionally to the braking belt is pulled down onto the braking belt.